Various sutureless heart valve prostheses have been considered for replacing diseased or defective native cardiac valves (e.g., the aortic valve). One such type of prosthetic heart valve includes a radially collapsible/expandable stent, which supports a set of valve leaflets. Typically, the stent is radially contracted during implantation of the prosthetic valve at the desired location. To optimize performance, the stent is sized such that, if unrestrained, it can expand to a diameter somewhat greater than the diameter of the annulus of the valve to be replaced and/or the vessel proximate to the native valve (i.e., in the case of an aortic valve prosthesis, the ascending aorta).
To ensure proper anchoring and operation of the prosthetic valve in situ, it is helpful to assess the size of the patient's anatomical valve annulus. The annulus includes dense, fibrous rings attached to the adjacent atrial or ventricular muscle fibers. In some valve replacement procedures, the physician excises the defective native valve leaflets to prepare the annulus for implantation of the replacement valve. Typically, physicians use a set of sizing obturators, which are provided by various heart valve manufacturers, to obtain an estimate of the diameter of the native valve annulus. These sizing obturators typically include a cylindrical body having a flat, annular flange thereabout. The physician typically advances the flange to a location adjacent the superior aspect of the valve annulus, but does not typically advance the flange to an intra-annular position. This process may require the physician to repeatedly introduce various sizing obturators to the valve annulus to obtain this size estimate. This procedure requires much time and effort and offers minimal accuracy. This procedure also relies significantly on the skill of the implanting physician, as proper sizing is largely based upon the skill and technique of the physician.